Numerous agents have been examined for their ability to prevent contrast-induced decreases in renal function. Among them the use of low-osmolarity, non anionic contrast agents, and prophylactic hydration have reduced the incidence of CIN. Administration of drugs such as calcium antagonists, theophyllin, dopamine and atrial natriuretic peptide does not prevent CIN. In some studies antioxidant agents like acetylcysteine and ascorbic acid seem to reduce the incidence of CIN.